This invention relates to a light-sensitive silver halide photographic material, particularly to a high sensitivity light-sensitive silver halide photographic material with little stain.
In the field of light-sensitive silver halide photographic materials, it has been practiced to add a spectral sensitizing dye for photography in the photographic emulsion constituting the light-sensitive material.
In preparation of silver halide emulsions, the procedure generally comprises passing through the steps of formation of silver halide grains, physical ripening, desalting and chemical sensitization, etc. During such steps, the timing at which a spectral sensitizing dye is added to the emulsion may be selected variously, but as the technique in the prior art, there is first the technique in which it is performed before coating after chemical sensitization, or before initiation of chemical sensitization or in the course of chemical sensitization as disclosed in U.S. Pat. No. 4,425,426. Further, secondly, as disclosed in U.S. Pat. Nos. 2,735,766, 3,628,960, 4,183,756, 4,225,666, Japanese Unexamined Patent Publications Nos. 26589/1980 and 184142/1983, there is the technique in which it is added in the course of forming grains (during physical ripening). Thirdly, as disclosed in Japanese Unexamined Patent Publications Nos. 103149/1986 and 196238/1986, there is the technique in which it is added in the latter half of grain growth when the shape of the grain is not substantially changed, and after formation of grains before the desalting step. However, the above first technique of the prior art has the problem that it can be applied only for the case when a dye having high sensitizing ability and strong adsorption power is used, because adsorption of the dye to silver halide is weak. The above second technique of the prior art may sometimes suffer from obstruction of normal crystal growth due to adsorption of the dye on the grain surface during growth, since a dye is added in the course of grain formation. Also, since the first to the third techniques of the prior art as mentioned above all perform formation of grains and adsorption of the dye, while having grains dispersed and adsorbed in a hydrophilic colloid, the amount of the dye adsorbed is insufficient and not satisfactory.
Also, the conventional light-sensitive material to which a spectral sensitizing dye is added has not sufficiently solved the problem of stain. Particularly, when the amount of the dye is not sufficient as described above, an attempt to increase the adsorption amount may sometimes result in pronounced stain.
Further, the light-sensitive material of the prior art involves the problem that the performance to the so called pressure blackening, in which blackening occurs under pressure generated, for example, when the light-sensitive material is bent, is not sufficient.
An object of the present invention is to provide a light-sensitive silver halide photographic material spectrally sensitized, which is a high sensitivity light-sensitive photographic material increased in the adsorbed amount of a spectral sensitizing dye, and yet with little stain and good pressure blackening performance.